1. Field of the Invention
This invention relates to microwave ovens and in particular to methods and apparatus for testing microwave leakage from such microwave ovens in the manufacture thereof.
2. Description of the Prior Art
In U.S. Pat. No. 3,693,084, Carl F. Augustine discloses a method and apparatus for detecting microwave fields, such as the leakage of microwave energy around the doors and the like of microwave ovens. The patentee discloses a power density meter which includes a first microwave detector which records both microwave and infrared radiation, and a similar second detector recording only infrared radiation. By measuring the difference in color levels of the detectors, the infrared energy contribution is cancelled. More specifically, the patentee teaches the use of a first reflector positioned one-quarter of a wave-length from the first detector to cause all of the incident microwave energy to be dissipated in a resistive film. A second reflector is positioned one-half wave-length from the second detector such that all of the incident microwave energy is reflected and none is absorbed by the resistive film. A circuit is provided for balancing the color levels of both detectors to provide a quantitative measurement of the incident microwave energy.
In another embodiment, apparatus is provided for forming holograms of the microwave distribution. A camera or other imaging apparatus is positioned to record an interference pattern and provide a transparency thereof. The image of the object is reconstructed by illuminating the transparency with coherent light.
The detector utilizes liquid crystal temperature sensitive film means adjacent the resistive layer for transfer of thermal energy from the resistive layer to the liquid crystal sensitive film means to provide a visible display representative of the temperature distribution.
Bernard P. Gollomp discloses, in U.S. Pat. No. 3,812,334, a high speed measurement system which correlates high speed, low resolution measurements with low speed, high resolution measurements. The apparatus provides high speed measurement of analog input signals and converts the analog input signals to a digital format at precise increments. The apparatus utilizes input signal ranging capabilities in effecting the desired correlation.
Steven H. Garrett discloses, in U.S. Pat. No. 4,229,796, a programmed controller for ultrasonic testing of turbine rotors and the like. The apparatus includes a programmed microprocessor based electronic controller adaptively coordinating the ultrasonic testing operations of an ultrasonic tester and associated drive unit and a selective one of a plurality of control modes wherein each control mode is conducted in accordance with observable test data and anomaly indications generated from the ultrasonic tester and drive unit during the testing operations.